Comments

3.5.7.17 -stable review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o <tytso@mit.edu>
commit 39c04153fda8c32e85b51c96eb5511a326ad7609 upstream.
Once we decrement transaction->t_updates, if this is the last handle
holding the transaction from closing, and once we release the
t_handle_lock spinlock, it's possible for the transaction to commit
and be released. In practice with normal kernels, this probably won't
happen, since the commit happens in a separate kernel thread and it's
unlikely this could all happen within the space of a few CPU cycles.
On the other hand, with a real-time kernel, this could potentially
happen, so save the tid found in transaction->t_tid before we release
t_handle_lock. It would require an insane configuration, such as one
where the jbd2 thread was set to a very high real-time priority,
perhaps because a high priority real-time thread is trying to read or
write to a file system. But some people who use real-time kernels
have been known to do insane things, including controlling
laser-wielding industrial robots. :-)
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
fs/jbd2/transaction.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)